1. Field of the Invention
The present invention relates to a camera, and in particular to an auxiliary lens for a compact camera.
2. Description of Prior Art
Since the camera has been invented, people like to use it to take a picture. Especially, when people are traveling, they always carry a camera with them. After a digital camera has been developed, it has been widely used because it features instant viewability and erasability.
Like the traditional film cameras, the digital cameras can be classified into two categories, i.e. Single Lens Reflex cameras (SLR) and cameras. Since the compact cameras are highly portable, cheap in price and user-friendly, they are the mainstream in the market.
However, the focal length of a fixed (un-interchangeable) lens equipped in a compact camera is approximately in the range of 35 to 105 mm, which is equivalent to the focal length of a 35 mm-type film camera. The minimum focus distance is more than 50 cm, so that such a compact camera cannot provide a function of close-up photography or a macro-photography. Therefore, if a user needs a close-up photography or a macro-photography, he/she has to use a bulky-and-expensive SLR camera or attach an auxiliary lens with the desired specification to the front of original lens of the compact digital camera. However, even though a high-quality lens is selected, it can only operate well when being connected to the camera properly. Therefore, in addition to the quality of the auxiliary lens and the camera, it is also an important issue to connect this auxiliary lens and the camera firmly and accurately.
The conventional structure for fixing an auxiliary lens onto a compact camera has a base fixed to the outer periphery of the lens of the camera body and a lens mount fixed to the auxiliary lens. A plurality of blocks on the base passes through notches on the lens mount corresponding to the blocks, and then these blocks and notches are combined with each other by rotation. An abutting base fixed between the auxiliary lens and the lens mount exerts a force to the blocks on the base in a direction toward the camera body, thereby tightly clamping the blocks between the lens mount and the abutting base. In this way, the tightness between the camera body and the auxiliary lens is enhanced. Although one end surface of the conventional abutting base is provided with a plurality of springs adjacent to the lens mount, and the top ends of these springs are each provided with an elongate pillar oriented horizontally with respect to the one end surface. The pillars are much closer to the lens mount than the one end surface. Therefore, when the base is combined with the lens mount by rotation, the blocks on the base will pass through the notches on the lens mount to touch the pillars on the abutting base. As a result, the pillars and the springs are compressed in a direction toward the auxiliary lens. After being compressed, the spring generates a reaction force toward the camera body, thereby tightly clamping the blocks between the lens mount and the abutting base. Therefore, the tightness between the camera body and the auxiliary lens can be enhanced.
However, since the spring is formed with a plurality of windings in a coil, its volume cannot be reduced easily and thus it is not suitable for a compact camera. After being used for a long time, the spring may suffer elastic fatigue, so that the damaged elements should be replaced frequently. Since the cost of replacing metallic elements is larger, it becomes an additional burden for the user. Alternatively, another conventional fixing means has a base fixed to the outside of the lens of the camera body and an auxiliary lens via the engagement between the corresponding inner and outer threads. However, the degree of connection of such a fixing means substantially depends on the depth of threads on the base and the auxiliary lens. The volumes of the base and the auxiliary lens of such a fixing means are usually not small, so that it is not suitable for the compact camera.
In view of the above, the Inventor provides the present invention to overcome the above-mentioned drawbacks based on his researches.